What we do?
We are a research group interested in the propagation of radio waves in the atmosphere. Our primary goal is development of signal propagation models for planning of advanced communication systems such as mobile networks.
In general, we are focused on research of the electromagnetic waves propagation in the Earth's atmosphere for the needs of radio systems planning. The aim is to find suitable signal propagation models for given environment and given application supported by both theory and experiments.
The area of the electromagnetic wave propagation for radio communication systems is comprehensive and diverse. Many factors influence the signal propagation, such as random phenomenon which is difficult to describe determinately (e.g. weather), local environment on the ground (e.g. urban areas) etc. That is why experimental observations and simplifications of general scenarios are unavoidable. Specific requirements on the appropriate propagation model are based on the actual application. Part of our activities also includes system level simulations. As an illustration some of our activities are listed below.
coordinates all activities in the Radiowave Propagation team at the Department of Electromagnetic Field.
is concerned with millimeter, submillimetre and terahertz propagation, systems and technology waves. He deals also with fiber and free-space optics. He has developed a new method of classification of rain events in the framework of wave propagation research for point-to-multipoint systems.
is focused on an application of neutron networks in the area of wave propagation in the troposphere.
is focused on wave propagation in time domain and Ultra Wide Band propagation, moreover deals with cognitive radio and connection of these two technologies. His latest research is focused on the wideband spectral sensing as an input to cognitive radio awareness process.
Luděk Šubrt (first man)
is concerned with modeling of indoor electromagnetic wave propagation. In the framework of this activity, he is developing a new 3D model for electromagnetic wave propagation predictions. His latest research is focused on the intelligent control of propagation environments for indoor wireless networks.
is focused on vegetation effects on land mobile satellite services.
is concerned with propagation of satellite signal into buildings in bands L, S. C. Morover he focuses on polarization antenna measurement.
Purpose of our research
Any radio system, i.e. system which uses wireless transmission of information, cannot avoid planning in terms of wave/signal propagation. A suitable model of signal propagation permits to choose type and location of antennas, optimize quality and reliability of the service, analyze interference etc. New prospective advanced radio systems represent new requirements on signal propagation research in various frequency bands.
Selected topics of our work
Simulation of the radio waves propagation
- Prediction of narrowband signal propagation in the sense of spatial determination of signal parameters based on descriptions of propagation environment and specific spatial arrangement mobile or fixed link inside or outside buildings
- Modeling of distribution of power levels, impulse response and other characteristics for wireless systems GSM, WLAN, UMTS, MIMO...
3D progation model
- Based on combination of deterministic and stochastic approach
- Considering surface roughness
- Material constants are substituted by probability parameters
- Calculations of spatial field distribution (signal covering), impulse response, angles of rays arrival to the receiver
Intelligent Control of Propagation Environment by Using Intelligent Walls
- Coverage control on the basis of the current users position by using Intelligent Walls
- Intelligent Walls contains sensors and active frequency selective surfaces
- Wireless cognitive network is able to observe, learn, optimize and make decisions on the basis of data gained from base stations and sensors mounted on the walls
- Cognitive control increases the system performance significantly
Influence of rain on systems working in the millimeter band
- Analysis and methodology for calculation of space- time statistics point-to-multipoint systems for specific area and in a given rainfall event
- Researching the effects of rain events on the behavior of systems using spatial diversity
- New methodic for classification spatial characteristics of precipitation depending on behavior of system type point-to-multipoint
Propagation Modeling of Shadowing by Vegetation for Mobile Satellite Services
With new requirements for wireless communication, broadcast quality and data amount, there is a demand to investigate the influence of vegetation shadowing on the propagation channel for terrestrial and satellite communication as well. Over the past decades, a huge number of experimental investigation focused on terrestrial services were performed covering many effects (season, frequency, measurement scenario, type of vegetation, etc.). In contrast to terrestrial investigation only a small number of performed works were focused on scenario for high elevation angle links, and if, only for limited scenario. Due to this a new measurement trials were proposed in order to investigation the influence of the vegetation shadowing for high elevation links and covering different measurement scenarios, relevant frequency bands and different seasons. Consequently, new attenuation models were developed covering two measurement scenarios. The first features one terminal within woodlands and covering wide range of elevation angles and frequency bands when vegetation is full in leaf and defoliated. The second introduces radio path obstructed by a single vegetative obstruction where both terminals are outside the vegetative medium and considering different frequency bands, seasons and shape of tree canopy.
Stratospheric platforms at high altitudes
- application of high-altitude platforms (HAP) for UMTS and WiMAX systems
- propagation prediction on 3G and WiMAX frequency bands for terrestrial and HAP network, authentication based on measurements
- using high-altitude platforms for covering the signal
- finding the largest possible cells for individual services
As the atmospheric conditions, expressed in terms of radio refractivity, can considerably influence the performance of radio communication links and radar systems, there is a need for reliable prediction of refractivity structure in the lower atmosphere. The usual methods of direct refractive index measurement by means of radiosounding and refractometers can usually only give a rough idea of the refractivity distribution. The basic disadvantage of the radiosonde, resulting from its occasional, although regular, launching, is that it is not able to provide a detailed idea of refractivity structure time development. In recent years, matched field processing methods representing indirect methods of refractivity structure sounding have turned out to be suitable alternative to direct means of measurement.
- Modeling of wave propagation in troposphere
- New methods of indirect determination of the height profile of refractivity
Propagation in the time domain
- Modeling pulse propagation in time domain
- The usesage of UWB for communication system and signal detection
- Application of cognitive radio for UWB systems
- UWB pulse shaping to maximize data rate and usage of the frequency specturm
There is a number of both national and international research projects focused on the radio wave propagation.
- Basic Research of Radiometeorology Properties of Tropospheric Ducting Layers by Using Artificial Intelligence Methods, Czech Science Foundation, grant no. P102/10/1901, 2010-2012
- Propagation Modeling of Shadowing by Vegetation for Mobile Satcom & Satnav Systems, Czech Ministry of Education, Youth and Sports, grant no. OC09074,2009-2012
- Building Penetration Measurement and Modelling for Satellite Communications at L, S and C-Band, ESA PECS project No. 98069, 2009-2010
In the area of high altitude platforms (HAP) we have cooperated with the University of York and others partners within the international project COST 297. In the area of experimental research of tropospheric propagation we cooperate with the Czech Metrology Institute. In the area of propagation modeling for high and low elevation links we cooperate with the University of Vigo and others partners within the COST Action IC0802.
- Kvicera, M. - Pechac, P.: Building Penetration Loss for Satellite Services at L-, S- and C-band: Measurement and Modeling, IEEE Transactions on Antennas and Propagation. 2011, vol. 59, no. 8, p. 3013-3021. ISSN 0018-926X.
- Kvicera, M. - Horak, P. - Pechac, P. - Perez-Fontan, F.: On a Definition of Building Penetration Loss for High Elevation Angles, IEEE Transactions on Antennas and Propagation. 2010, vol. 58, no. 12, p. 4115-4118. ISSN 0018-926X.
- Zvanovec, S. - Pechac, P: Validation of Rain Spatial Classification for High Altitude Platform Systems, IEEE Transactions on Antennas and Propagation, Accepted December, 2010.
- Subrt, L. - Pechac, P.: Semi-Deterministic Propagation Model for Subterranean Galleries and Tunnels, IEEE Transactions on Antennas and Propagation. 2010, vol. 58, no. 11, p. 3701-3706. ISSN 0018-926X.
- Urban, R. - Grace, D. - Pechac, P.: Impulse Radio UWB Pulse Shaping for Cognitive Radio Applications, Springer Wireless Personal Communications, DOI: 10.1007/s11277-010-0158-6, Accepted 2010.
- Valtr, P. - Pechac, P. - Kvicera, V. - Grabner, M.: Estimation of the Refractivity Structure of the Lower Troposphere from Measurements on a Terrestrial Multiple-Receiver Radio Link, IEEE Transactions on Antennas and Propagation. 2011, vol. 59, no. 5, p. 1707-1715. ISSN 0018-926X.
- Holis, J. - Grace, D. - Pechac, P.: Effect of Antenna Power Roll-Off on the Performance of 3G Cellular Systems from High Altitude Platforms, IEEE Transactions on Aerospace and Electronic Systems. 2010, vol. 46, no. 3, p. 1468-1477. ISSN 0018-9251.
- Horak, P. - Kvicera, M. - Pechac, P.: Frequency Dependence of Attenuation Due to Vegetation for Satellite Services. IEEE Antennas and Wireless Propagation Letters. 2010, vol. 9, p. 142-145. ISSN 1536-1225.
- full list